Abstract: Seagrass is a valuable component contributing significantly to coastal productivity and stabilising sea floor sediments in the shallow coastal marine ecosystems. The present field case study was conducted in a monospecific patch in an intertidal seagrass bed in Port Dickson, Malaysia. Shoot density and biomass of Thalassia hemprichii were measured using 20×20 cm quadrats. Leaf growth and productivity of T. hemprichii were studied using leaf-marking method. During low tide period the habitat of this species was observed by snorkeling. The mean shoot density of T. hemprichii was 632.14×113.77 shoots/m2, with mean above ground biomass measured at 13.87×1.17 g AFDW (ash free dry weight)/m2 and mean below ground biomass 40.19±7.93 g AFDW/m2. The mean leaf growth was 7.04×1.35 mm/shoot, where maximum leaf growth was recorded 11.45 mm/shoot. The mean leaf production was 0.56×0.17 g AFDW/m2/day, where the maximum leaf production was measured at 1.00 g AFDW/m2/day. Turnover rate and relative production rate (RPR) were measured at 3.68×0.79 percent/day and 0.07×0.03 g/g AFDW/day, respectively. Plastochrone interval of T. hemprichii leaf (PIL) during the study period was 12.03×1.01 days. Leaves of T. hemprichii beneath the shading of macro-algae (Sargassum sp.) were comparatively longer than those existing without such shading condition. There are 8-19 horizontal rhizome nodes within two shoots and this indication that two shoots of T. hemprichii were separated at this distance.